Tobacco, alcohol and opioid use disorders threaten the health of HIV-infected patients. What if evidence-based counseling and medication treatments for tobacco, alcohol and opioid use disorders (herein referred to as addiction treatments) were routinely provided in HIV clinics? Implementation Facilitation is an established and reproducible strategy to increase the uptake of evidence-based treatments. It is a multi-component intervention that assesses key stakeholder's (administrators, providers, patients) needs and provides a tailored implementation strategy using an external facilitator, local champions, provider education, academic detailing, stakeholder engagement, performance monitoring and feedback, formative evaluations, learning collaborative and program marketing to implement evidence-based treatments. Our goal is to evaluate the impact of Implementation Facilitation on the use of addiction treatments in four large HIV clinics. We will use the PARiHS (Promoting Action on Research Implementation in Health Services) Implementation Science framework in a Hybrid Type 3 study that allows for simultaneous evaluation of the implementation and its effectiveness. We will use a stepped wedge design that randomly assigns the order in which the clinics receive Implementation Facilitation. Our aims are: Aim 1-Among key stakeholders, to use mixed methods to identify evidence, context and facilitation-related barriers and facilitators to the integration of addiction treatments to help tailor an Implementation Facilitation for each clinic: Aim 2-To assess the impact of Implementation Facilitation on: a) organizational and provider readiness to deliver addiction treatments, b) the provision of addiction treatments, c) changes in organizational models used to deliver addiction treatments; and Aim 3- To evaluate the impact of Implementation Facilitation on antiretroviral receipt, viral suppression, VACS Index (a validated measure of mortality risk) and retention in HIV care among patients eligible for addiction treatment. The novel aspects of this proposal include: 1) the use of Implementation Facilitation to address a range of disorders, rather than a single substance use disorder in HIV clinics, 2) incorporation of administrator, provider and patient input into the implementation of addiction treatment in HIV clinics, 3) a hybrid implementation- effectiveness design for assessing short and long-term uptake of addiction treatments in HIV clinics, 4) a focus on organizational models that ensure that there is integration of addiction treatments at the clinic level but allows flexibility as to who provides these treatments based on stakeholder input and the abused substance, and 5) the use of the VACS Index that better reflects the health benefits of abstinence than a focus on viral load which may be suppressed in patients on antiretroviral treatment despite ongoing tobacco, alcohol or opioid use. The Working with HIV Clinics to adopt Addiction Treatments using Implementation Facilitation (WHAT IF?) study holds exceptional promise of identifying an effective strategy to increasing the uptake of addiction treatments into HIV clinics thereby reversing their devastating impact on morbidity and mortality.